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XJ's Dead! "No Bus" message on Odometer

X

xjralfy

NAXJA Forum User
Location
Phoenix, AZ
Well, I went up to Crown King this weekend and made it back ok, but this morning she wouldn't start. Battery's fine and the starter turns over, but she won't start. My instrument cluster lights up but the guages don't move. After about 10 seconds the message "No Bus" appears on the Odometer and the Check Engine light comes on.

Searching around I found that the message "no bus" usually means a bad connection to the instrument cluster. So, i pulled the cluster and there were two "connectors" on the back. I cleaned both and even put some dielectric grease on but the issue remains. My neighbor hooked up an OBD II reader but all it would display was "Link Error". He said my computer probably went bad.

Anyways... I'd really hate to have her towed to the dealer. Any other ideas?

Thanks, Ralfy
2001 XJ
 
Check fuses & relays, and don't forget to include the PDU under the hood (passenger side, on top, next to the fender) in your search. Something has likely blown or worked its way loose - total computer failure is *relatively* rare, especially on newer XJs.
 
Sounds like a shorted sensor taking down the bus from the PCM to the cluster. Try unplugging your sensors until the cluster becomes active on the bus again. Crank sensor and either O2 sensor are likely culprits.
 
hey, i jave a similar problem, i'll be doing 45-80 mph down the highway when the tack and speedo just go slack and lay down displaying nothin. as well i get the "no bus" display on the odometer..so now every time it happens i just give her a little tap on the brake and suddenly everything just comes "back to life" per say. haven't figured it out but was told it sounds like a "loose speedo connection". i dont know that it would keep the jeep from starting but you never know.
 
check the big fat connector (C101 IIRC) under the dash that brings the harnesses together. I know that 98 had a service buleting on it, might have been affecting more models/years.
 
WNC Custom Jeeps said:
Sounds like a shorted sensor taking down the bus from the PCM to the cluster. Try unplugging your sensors until the cluster becomes active on the bus again. Crank sensor and either O2 sensor are likely culprits.
Click to expand...

Check your crank sensor, known to fail in this way. WNC is correct.
 
All of those are good suggestions. Here is another: The reason your dash is displaying No buss is cause a controller is taking it down. You didnt say what year you have but you most likely have a PCI buss system. It consists of 2 wires that send a small voltage to each one of the controllers to relay info. If a controller locks up it will take them all down. The instument cluster is on the bus, I usually go for that first. Usually unplugging the modules and plugging them back in will wake it up. In this case though it sounds like the cluster isnt the culprit. However, next time dont pack it with dialectric. What you need to do is when the NO Buss is displayed (meaning problem is active) Go around to each controller and unplug it and re plug it one by one and which ever one changes the condidtion is the one locking up your buss. There are possibly lots of modules on the buss i.e. Radio, BCM, PCM, Cluster, ACM, TCM not sure what your vehicle has but I may be able to get you a wirring diagram.
 
holeshot said:
You didnt say what year you have but you most likely have a PCI buss system. It consists of 2 wires that send a small voltage to each one of the controllers to relay info.
Click to expand...


Close, but no cigar. PCI bus is one wire, CCD bus or the new CAN bus are both 2 wires. Mostly good info though.


Back on subject, just disconnect the crank sensor and see if the display goes back to normal.
 
First off... thanks for all the ideas. And yea, I'd have a full signature w/ my XJ info filled out but can't seem to find the signature link.

Ok, the general problem seems to be the Computer or something going to the Computer and causing it to lock up. I’ll check out the sensors starting w/ the Crank Position, but to be honest I only know where the O2 and the Neutral Safety Switch ones are located. I’ve been meaning to get a FSM but only have the Haynes manual, which IMO is worthless.

Could some please give me a brief description of where the following are located?

Crank Position Sensor-
Crank Case Ventilation-
Manifold Absolute Pressure-
Throttle Position Sensor-
Transmission Control Unit-

Thanks, Ralfy
2001 XJ
 
holeshot said:
What you need to do is when the NO Buss is displayed (meaning problem is active) Go around to each controller and unplug it and re plug it one by one and which ever one changes the condidtion is the one locking up your buss. There are possibly lots of modules on the buss i.e. Radio, BCM, PCM, Cluster, ACM, TCM not sure what your vehicle has but I may be able to get you a wirring diagram.
Click to expand...

BCM?
PCM?
ACM?
TCM?
:banghead:

Yea, if you've got a wiring diagram to an 01', it would be much appreciated.

Ralfy
 
Crank sensor. Look at the bell housing, drivers side near the top, about the 10 o'clock position. Follow the wire to the connector on top of the intake manifold near the firewall end. Don't worry about the other sensors untill you check this one. Just disconnect the sensor and then see if the display goes back to normal. If it does, buy a crank sensor.
 
It is threads like this that I ponied up the bucks and joined this group. Great help guys, and keep up the good work!
Mine was a CPS problem. They do some wierd things when they are going out.
 
xjralfy said:
BCM?
PCM?
ACM?
TCM?
:banghead:

Yea, if you've got a wiring diagram to an 01', it would be much appreciated.

Ralfy
Click to expand...
Body Control Module
Powertrain Control Module
Airbag Control module
Transmission Control Module
 
Bryan C. said:
Close, but no cigar. PCI bus is one wire, CCD bus or the new CAN bus are both 2 wires. Mostly good info though.


Back on subject, just disconnect the crank sensor and see if the display goes back to normal.
Click to expand...

Ahh yes good call Bryan C. PCI was only one year right? 2001??? It had that cool little junction port under the dash. Thanks for the correction.
 
Bryan C. said:
Crank sensor. Just disconnect the sensor and then see if the display goes back to normal. If it does, buy a crank sensor.
Click to expand...

Well, i disconnected it and the guages went back to normal. So then I decided to remove it....

Hypothetically speaking... Lets say one of the bolts managed to fall through the opening and into the bell housing....

On a scale of 1 to 10... How fuct am I?
 
xjralfy said:
Well, i disconnected it and the guages went back to normal. So then I decided to remove it....

Hypothetically speaking... Lets say one of the bolts managed to fall through the opening and into the bell housing....

On a scale of 1 to 10... How fuct am I?
Click to expand...

unless you can fish it out through that hole I believe #11 would be appropriate.
 
You can take the inspection cover off the bottom of the bellhousing and fish it out with a pocket magnet. It has happened to me before, no big deal at all.

Glad to be of help on this one...
 
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